|Molecule Type||Antigen Expression||Molecular Weight|
Min / Max
|Lineage Restricted Molecule|
Type 1 glycoprotein
|45 / 45|
|CD1b is expressed on cortical thymocytes and with less intensity on CD4+ and CD8+ thymocytes. CD1 is absent on mature peripheral blood T cells but intracytoplasmic expression is detected on activated T lymphocytes. CD1b is not detected on normal B cells. However a proportion of B cell malignancies express CD1b isotypes. Low levels of CD1b are present on Langerhans cells (LC). After migration from the epidermis or on dendritic cells from the dermis, expression of CD1b is increased. CD1b is detected in myeloid leukemias. These molecules are induced on monocytes by treatment with the granulocyte-macrophage colony stimulating factor (GM-CSF) alone or by GM-CSF plus IL-4. |
|MOLECULAR FAMILY NAME: Belongs to the immunoglobulin supergene family.|
CD1b is a single-pass type-1 a chain glycoprotein. It contains an extracellular domain which contains 3 domains, α1, α2 and α3 each 90 aa, 3 potential N-glycosylation sites in domains α1 and α2, a transmembrane domain and a short cytoplasmic domain containing a tyrosine-based motif (YXXZ) which is essential for access to late endosomes and lipid binding. It is non-covalently associated with b2 microglobulin and has structural similarities to MHC class I molecules.
The alternative splicing yields 2 different isoforms which are tissue specific and give rise to membrane attached and soluble forms. Multiple splicing patterns have been found for all CD1 transcripts except for CD1b. CD1b revealed only a single membrane RNA product which has been identified..
Potential N-linked glycosylation sites are 3 in CD1b.
|LIGANDS AND MOLECULES ASSOCIATED WITH CD1b|
Some T cells recognize antigen in a CD1-restricted manner. Mouse NK1+ T lymphocytes, which have a restricted TCR repertoire, recognize murine CD1, although there is conflicting data. Antigens presented by human CD1b were identified as microbial lipids. A recombinant form of the murine CD1 binds synthetic peptides with micromolar affinities. It showed a preference for longer peptides than seen for class I and resembles class II peptide binding.
|CD1b associates with β2 microglobulin and non-peptide Ag presentation. Most CD1b molecules are located intracellular in acidic and late endosomes are where lipid antigen is loaded onto CD1b. CD1s have been demonstrated to restrict T-cell responses to non-peptide lipid and glycolipid antigens. CD1 molecules could be involved in the delivery of signals for lymphocyte activation. Some anti-CD1 mAbs produced inhibition of bacterial superantigen thymocytes proliferation. On peripheral blood mononuclear cells (PBMC), depending on the epitope recognized by the mAb, an inhibitory or enhanced effect on the proliferative response to the phosphokinase C (PKC) activator phorbol myristate acetate (PMA) has been observed. The expression of CD1 molecules on thymocytes has been related to a role in thymic T-cell development. NK1+ cells a subset of T cells found in high frequencies in the mature compartment of the mice thymus are involved in the development of NK cells. These cells, found in high frequencies in bone marrow and liver, have CD1 molecules as their ligand. It has been postulated that through their NK-like activity, the liver is actively involved in the peripheral cell deletion of T cells arriving from the intestine through the portal vein. By this mechanism, these cells may be involved in the induction of oral tolerance. |
BIOCHEMICAL ACTIVITY: No information.
DISEASE RELEVANCE AND FUNCTION OF CD1b IN INTACT ANIMAL: No information.
|CD1 genes, except CD1b, are transcribed in the same direction and all lack classical promoter elements.|
MOLECULAR INTERACTIONS -
PROTEINS AND DNA ELEMENTS WHICH REGULATE TRANSCRIPTION OF CD1b: No information.
SUBSTRATES: No information.
ENZYMES WHICH MODIFY CD1b: No information.
CD1b is homologous to histocompatibility antigens but is not genetically linked to the histocompatibility locus.
Database accession numbers
Revised June 25, 2008